Uncover new dimensions of isotope ratio analysis with Thermo Scientific Orbitrap MS technology

Significance of the Topic

The development of advanced isotope ratio mass spectrometry workflows is critical for modern analytical chemistry. By preserving intramolecular isotopic detail, researchers gain deeper insights into biochemical pathways, environmental cycles, and material provenance. Electrospray ionization (ESI) coupled with high-resolution Orbitrap technology extends traditional IRMS capabilities to liquid samples, enabling multi-element and position-specific isotope analysis without extensive sample conversion.

Objectives and Study Overview

This article introduces a novel approach to isotope ratio analysis using Thermo Scientific™ Orbitrap Exploris™ MS. Key objectives include:

• Demonstrating direct measurement of intact molecular isotopologues for natural-abundance and enriched samples.
• Developing methodologies to optimize detection of minor isotopologues via “without M0” scan strategies.
• Establishing data processing workflows for accurate δ-value calculation against international reference materials.

Methodology and Instrumentation

The workflow comprises two sample introduction modes: dual syringe inlet for high-precision bracketing of sample and reference, and automated in-flow injection via Vanquish™ Neo UHPLC for higher throughput. Intact molecules are ionized by ESI, filtered by Advanced Quadrupole Technology, optionally fragmented in an ion-routing multipole, then analyzed in the high-field Orbitrap. The “without M0” method shifts the m/z scan window to exclude the dominant monoisotopic ion and amplify signals from singly and multiply substituted isotopologues.

Used Instrumentation

• Orbitrap Exploris™ 120/240/480 mass spectrometer with ESI and Advanced Active Beam Guide
• Dual Syringe Inlet system with diverter valve
• Vanquish™ Neo UHPLC System for in-flow injection
• Tune New Generation Software for source optimization
• Xcalibur™, FreeStyle™, and IsoX™ software packages for instrument control, data visualization, and isotopologue extraction

Main Results and Discussion

Analysis of nitrate demonstrated the ability to detect 20 stable isotopic variants in a single measurement. Using “without M0” acquisition improved precision for minor isotopologues by avoiding detector saturation from the base peak. Combined data from standard and shifted scans allowed calculation of accurate isotope ratios (e.g., 15N/14N, 17O/16O, 18O/16O) at sub-permil uncertainty. Dual inlet bracketing ensured robust comparison against reference materials (USGS-32, USGS-34, USGS-35), yielding linear δ-value correlations and reproducible results over multiple blocks.

Benefits and Practical Applications

This comprehensive Orbitrap-based IRMS approach offers:

• Reduced sample preparation by eliminating gas-conversion steps
• Preservation of intramolecular isotopic distributions for position-specific studies
• Enhanced sensitivity for low-abundance isotopologues
• Accelerated analysis times (6–15 min per sample)
• Versatility across environmental, geochemical, biochemical, and food-authenticity applications

Future Trends and Potential Applications

Emerging directions include:

• Expansion to other polar and non-polar biomolecules, including peptides and metabolites
• Coupling with micro- and nano-flow UHPLC for limited sample volumes
• Integration with automated data pipelines and machine-learning for isotopic pattern deconvolution
• Development of new geochemical proxies based on multi-element clumped-isotope analysis
• High-throughput screening of provenance markers in food, pharmaceuticals, and forensic samples

Conclusion

Thermo Scientific™ Orbitrap Exploris™ Isotope Solutions introduce a versatile, high-precision IRMS workflow for intact molecular ions. By combining ESI soft ionization, dynamic scan strategies, and robust software tools, the method retains intramolecular information, enhances detection of rare isotopologues, and streamlines analysis. This platform broadens the scope of isotope ratio studies and promises new insights in environmental, biochemical, and industrial research.

References

No external literature references were provided in the source document.